It is the long-term objective of this proposal to develop a cost-effective robotic rehabilitation machine that safely improves and accelerates a person's recovery outcome after a stroke or traumatic brain injury by enhancing neural rewiring. By the end of Phase-ll, a human-scale machine will be built and validated that is both safe and enables full and precise quantification of spatial paths and force/torque control and history. Phase III will focus on FDA clearance for these indicated procedures. The performance of this machine will broaden application of the promising results of recent clinical work at the Rehabilitation Institute of Chicago (RIG) in trajectory-error amplification and work at Carnegie Mellon and the University of Pittsburgh in exploiting disturbed perception. Common among these studies is the notion of creating or amplifying a patient's trajectory errors relative to a visual target. It is believed that these techniques motivate the patient to rebuild the neural-muscular structure to function better at reaching and grasping during the crucial few months after the trauma or stroke. The use of a sophisticated robotic machine is absolutely essential to this type of therapy. Machines of this type (aka haptic devices) are human-centric but tend to be too small in size to enable large limb rehabilitation. Simply increasing the scale of the machine addresses both the reach and force/torque capabilities of the machine. However, there are two drawbacks when these machines are scaled up to accommodate an adult human's full limb motions: 1. Larger force capability and reach may offset the therapeutic benefits. 2. Larger machine inertias mechanically filter, and therefore dull, the perceptual quality of contacting hard surfaces. Relevance to Public Health: Especially in an aging population, the frequency of brain/neural injuries due to stroke or trauma is growing. By immersing a patient in a special robot-generated virtual environment, it may soon be possible to reverse neural stroke or trauma damage somewhat during the critical first few months after injury. [unreadable] [unreadable]